1. Field of the Invention
The invention relates generally to forming a thin metal film on a substrate and more particularly to forming a single crystal epitaxial metal film on a substrate.
2. Description of the Prior Art
There is a growing class of devices that require thin, high quality, single crystal epitaxial films of iron or other metals for their operation. Examples include magnetic or bubble memory devices, magneto-optical switches and microwave terminators.
In order to form a single crystal epitaxial metal film the crystal structure of the substrate surface must be of very high quality. This surface quality of the substrate is determined by an examination utilizing Auger spectroscopic and low energy electron diffraction (LEED) techniques. Subsequent to the forming of the film its crystallinity must be examined by these same examination techniques to determine whether the film has formed into a single crystal. These examining techniques must be performed in an ultra high vacuum environment to be effective. If the film were removed from the vacuum prior to examination the introduction of contaminants would degrade the quality of the film and reduce the accuracy of the examining techniques.
Presently, these single crystal epitaxial metal films are formed in a high vacuum chamber by molecular beam epitaxy (MBE). The examination of the substrate and metal film is carried out in-situ without breaking vacuum. However, the MBE method of forming the metal films is very slow and only suitable for substrates with a small surface area.
Another method for depositing metal films is metalorganic chemical vapor deposition (MOCVD). The standard MOCVD method is performed by introducing a metalorganic vapor into a carrier gas and exposing a heated substrate to the metalorganic vapor-carrier gas mixture. This method is faster than MBE and more effective with large area substrates. However, the method is not performed in a high vacuum environment due to the presence of the carrier gas. Thus, the standard MOCVD method does not allow in-situ characterization of the deposited metal film by such means as Auger and LEED analysis.